1. Technical Field
The present invention relates to a touch screen and a method for driving the same.
2. Description of the Related Art
Development of a smart mobile system has actually contributed to a rapid change in all aspects of our lives. Things possible only in a specific space have become possible regardless of time and place. For example, work conducted by an e-mail during movement or work of accessing the Internet to search information has been now naturally performed routinely. The reason is that miniaturization of a system has become possible and a memory having a high capacity of a gigabyte or more has been implemented by a single chip, due to the development of a semiconductor manufacturing technology, and a high performance and low power consumption processor technology has become possible due to the development of a circuit technology. A revolution of the mobile system as described above has been implemented through a smart phone or a tablet personal computer (PC). The mobile system has become miniaturized, advanced, and smart through innovation of an input device. Input devices such as a keyboard and a mouse that have been used in a fixed type computer may be restrictions fatal to the mobile system due to a physical limitation such as a size thereof, a weight thereof, or the like. However, these restrictions may be effectively solved by a touch screen. The touch screen does not require an additional space and enables an effective and advanced input such as a multi-touch. Since the touch screen is operated by a contact between a finger and the touch screen, a user may naturally feel a tactile feedback when the touch screen is touched.
For example, since Apple's iPod Touch has emerged, a touch interface has been used as a user input means in various mobile devices such as iPhone, iPad, Galaxy, Galaxy Note, and the like.
Regardless of a form of a change in an appearance of a mobile system that will evolve in the future, the evolution of an input system for developing the mobile system has been continuously conducted.
As a scheme of sensing a touch of the touch screen as described above, there are mainly two schemes, that is, capacitance sensing and electromagnetic resonance (EMR) sensing.
First, in the capacitance sensing, a change of capacitance generated at the time of a touch by a human body or a specific object is sensed. A difference between a minute change value in capacitance generated when the human body touches a surface to be touched and a set value is sensed to generate a final output. A touched portion in a touch sensor is made of a metal. When a current flows to the metal portion, the touch sensor enters an operation standby state. In this case, when the user touches a switch with his/her hand, electricity flows in the human body, such that a voltage is changed in a short time and an output of an internal circuit is changed in response to the changed voltage.
Meanwhile, in the EMR sensing, a coil embedded in a pen transmits and receives a frequency in a specific region generated in a terminal sensor in an electromagnetic induction scheme to sense writing pressure, speed, coordinate information of the pen. More specifically, when very minute energy is induced in a magnetic field generated in a surface sensor board by a resonant circuit of the pen, the resonant circuit of the pen may again return a magnetic signal to the surface sensor board using the energy. A surface may be configured of an electronic pen in which a sensor unit formed of a coil and the resonant circuit are embedded.
Since the capacitance sensing and the EMR sensing are performed by different methods as described above, it is difficult to implement the capacitance sensing and the EMR sensing in a single touch screen.
The following Prior Art Document (Patent Document) relates to a touch screen. More specifically, this Patent document has disclosed a method of implementing a hybrid type touch panel by combining a projective capacitive touch panel and a pressure-sensitive touch panel with each other.